1. Field of the Invention
The present invention relates to a display screen turning apparatus, and more particularly, it relates to a display screen turning apparatus comprising a base portion for placing a display screen portion.
2. Description of the Background Art
A display screen turning apparatus comprising a base portion for placing a display screen portion or the like is known in general, as disclosed in Japanese Patent Laying-Open Nos. 6-225245 (1994), 2004-258055 and 2004-304679, for example.
The aforementioned Japanese Patent Laying-Open No. 6-225245 discloses a projection television (display) comprising a tilt mechanism (display screen turning apparatus) including a tilt drive motor fixed on an upper surface of a tilting base (base portion), a tilt gear train (transmission gear portion) and an arcuate rack gear fixed with a gear portion with the bottom down on the bottom of the projection television body (display screen portion), a plurality of tilting rollers rotatably provided on the bottom of the projection television body and a tilting guide provided on the upper surface of the tilting base (base portion). In this projection television (display), the projection television body (display screen portion) is placed on the tilting base (base portion) in a state where the plurality of tilting rollers are rotatably fitted into grooves of the tilting guide, and the driving force of the tilt drive motor is transmitted to the rack gear through the tilt gear train (transmission gear portion) located below the rack gear so that the projection television body (display screen portion) can turn on the tilting base (base portion) in a vertical direction.
The aforementioned Japanese Patent Laying-Open Nos. 2004-258055 and 2004-304679 each disclose an electric rotary mechanism for a display comprising a tilt mechanism including a horizontally long support frame having a groove and rotatably supporting a support plate provided on a lower back surface of a display along with the display in a vertical direction, an electric motor and a reducing gear (transmission gear portion) mounted on the support frame in an upright direction, a rotating arm with a first end fixed on a drive shaft closer to the reducing gear (transmission gear portion) and a coupling arm with a first end rotatably coupling to the support plate. In this electric rotary mechanism for a display described in Japanese Patent Laying-Open Nos. 2004-258055 and 2004-304679, second ends of the rotating and coupling arms are rotatably coupled to each other with a shaft member and the driving force of the electric motor is transmitted to the rotating arm, the coupling arm and the support plate in this order through the reducing gear (transmission gear portion) so that the display (display screen portion) can turn on the support frame along with the support plate in a vertical direction.
In the projection television (display) comprising the conventional tilt mechanism (display screen turning apparatus) proposed in the aforementioned Japanese Patent Laying-Open No. 6-225245, however, the own weight of the projection television body (display screen portion) is conceivably applied to the tilting base (base portion) through the tilting rollers and the tilting guide, while the rack gear meshes so as to cover the tilt gear train (transmission gear portion) from above and hence the load from the projection television body (display screen portion) is conceivably applied also to the tilt gear train (transmission gear portion). Therefore, it is disadvantageously difficult that the tilt gear train (transmission gear portion) smoothly transmits the driving force of the tilt gear train (transmission gear portion), due to the load applied from the projection television body (display screen portion).
In the conventional electric rotary mechanism for a display proposed in each of the aforementioned Japanese Patent Laying-Open Nos. 2004-258055 and 2004-304679, the reducing gear (transmission gear portion) is conceivably designed such that a plurality of gears having a large gear ratio are combined with respect to the electric motor driving at a high speed to reduce its speed by a low rotational speed in order to turn the display (display screen portion). Therefore, in view of sizes of the members of the reducing gear (transmission gear portion) including the electric motor, it is disadvantageously difficult in design that the reducing gear (transmission gear portion) and the electric motor are provided on the horizontally long support frame in an upright manner.